Gangnu is a pavilion-like structure positioned on a relatively high part of the fortress walls, where troops were able to rest and keep watch on the surrounding areas. During extraordinary situations, it also served as a command post. One of four such pavilions, Seonamgangnu is located at the southern end of Yongdo, a passageway along the outer perimeter of the fortress used for patrolling, and situated on the southern slope of Mt. Paldal. It was built between April 16 and July 20, 1796 (the 20th year of King Jeongjo’s reign). Concerning the inscription “Hwayangnu” in the frame hung on the wall, “hwa” means Hwaseong and “yang” the south of the mountain.